Explaining the 3-4 Defense

        It occurs to me that unless you've played football, you probably have no idea how a defense really works. Hell, many of you probably don't care, in which case feel free to ignore this one. But for the small percentage of crazies out there like me, you might find this interesting and helpful. I'd like to try to explain some of the basics so that when you watch your team on Sunday, you can understand the little things that guys like Casey Hampton do to make every play work.  However when you consider the fact that anyone reading this post is probably a Steelers fan, it becomes slightly more complicated because then we’re talking about a Dick LeBeau defense.  I'm not trying to pretend I understand his defense, because I don't. To be honest, I doubt even Mike Tomlin fully understands the complexities that LeBeau has developed through decades of experience. However, the basics of his system are no different than any other 3-4 defense.  Therefore, if you have any desire to understand not just the terminology, but the some of the lighter intricacies of what is going on before your eyes on Sundays, this article may just bring some clarity.


        The biggest thing I want people to take from this is that every player plays a pivotal role in a defense's successes and failures on any given play. I think that most Pittsburgh fans realize at this point that the NT in a 3-4 plays a huge role as a sort of anchor. Most know his primary job is to take up blockers but it is slightly more complicated than that. In a 3-4 defense, the NT lines up directly over the center.  The idea here is that the NT is expected to be able to win a one on one battle against any lineman, meaning that it takes multiple blockers to stop him. More blockers on him means that there are less to address the linebackers. If a nose doesn't have that type of capability, the defense can't succeed.  This shouldn't imply that any fat guy can step in and be a sort of "brick wall."  A nose should be immovable, but that doesn't mean he's unathletic. If he's just in the way, an offense won't feel the need to place multiple guys on him, which defeats the purpose. They have to be able to collapse the pocket, win one on ones and take up space by demanding the attention of as many as three linemen at once. That's why there is such a premium on guys like Hampton. The problem is that there just aren't many guys on the planet with the combination of size and strength that is required.

        Next I want to reiterate that if the offense comes with as many blockers as you have defenders, there is nobody left to tackle the running back. If each offensive player wins their battle with a well designed play, an explosive play usually results. One of the fundamental principles of the pass to run philosophy, is to get the defense to back the extra defender up, in essence even up the box count for the offense. With a hat on a hat, plus one (the ball carrier), it isn’t hard to run if they can execute. There are lots of different offensive strategies to running, but really, this principle is at the core of it all.

        On defense the concept is essentially the same, a hat on a hat, plus one. There must be an extra player that the offense can’t dedicate blockers to in place to tackle the running back. (Imagine a scenario where the offense has 3 blockers and a ball carrier. the defense would then want at least 4 guys. 3 to take blockers, one to make the play. This is what a hat on a hat plus one implies.) When the offense blocks a corridor into the secondary, an explosive play results more often than not. Even with the best backs, explosive plays are rare when the back has no blockers beyond the line of scrimmage.

        The ball can’t go through an offensive blocker, it has to go around him. The defenses job is to close each of the gaps between the lineman. In a 1 TE set, there are 7 gaps for the defense to control. Some players control 1 gap, some players control 2. Some players don’t control any. Most systems and play calls will ask at least 1 linebacker to control a gap. Most also leave 1 linebacker or safety with no gap responsibilities. (For the Steelers that guy is usually Lawrence Timmons or Troy Polamalu) He is free to flow to the ball and make plays. When the defense has all gaps covered, the best the offense will muster on a run play is how much downfield push the line got. If there is a crack, and the back gets through, there is a linebacker and/or safety to make the tackle that has no gap responsibility. 

        Now, let's break down each position, starting with defensive ends. They're much different than 4-3 ends, who are typically pass rushers, like Julius Peppers, Dwight Freeney or Jared Allen. In a 3-4 however the ends are responsible for the gap between the OG and the OT, and possibly also for the gap outside of the tackle (on the weak side, if the OT blocks the OLB, the DE has to be aware of, and help out on that mismatch and help cover that gap). The end will typically be single blocked by either the OG or OT, though it is common for the OT to give the OLB a shove than turn to help the G double team the DE.  There are slight differences between the two ends. Offenses align their TE on the right side more often than the left. This makes the defensive left the strong side more often than the weak. Most offenses place their better run blockers on the right side, therefore most offenses run to the right more than the left. The defensive left gets run at with better run blockers than the defensive right. To counteract this the LDE is typically bigger and stronger than the RDE, and a better run defender. The opposite is true with the pass, and the RDE is typically a better pass rusher than the LDE, as offenses typically put their better pass blockers on the left side, the defensive right. Which makes sense when you think about the idea of a blindside OT.  Defenses prefer to have their best pass rushers coming from the side of the QB's non throwing arm. Since most QBs are right handed, generally speaking, the pass rushers will rush from the QBs left (The defensive right) so the the blindside tackle usually plays on the left. For the Steelers that means that when they had Aaron Smith and Brett Keisel, Smith was the better run defender and Keisel the better pass rusher, which makes a lot of sense when you consider how poorly the run defense was without Smith in the lineup in 2011.


        Next let's talk about the outside linebackers. There are no designated strong side (TE side) and weak side outside linebackers, as most 3-4 coordinators prefer right and left, keeping guys on the same side of the field. In the Steelers defense James Harrison is the ROLB and Lamarr Woodley is the LOLB.  Each OLB is responsible for the outside gap, meaning the back should not be allowed to bounce the play outside. The OLB on the TE side might also be responsible for the gap between the TE and OT depending on the play call.  The two positions are generally the same, though typically, as is true of the defensive ends, the LOLB will be the better run defender and better in pass coverage while the ROLB will be the better pass rusher.

        There are two distinctly different inside linebacker positions, the strong side inside linebacker (SILB) and the weak side inside linebacker (WILB). The SILB is called the BUCK and the WILB, the MACK. Unlike the OLB’s, the ILB’s do change sides based on which side the TE is on. The BUCK and MACK have very different skill sets as it relates to the run.  The buck is a banger. Remember one of the initial premises I made, a back with no blockers isn’t going very far. The buck eliminates the blockers. If there is a guard coming through, mix it up with the guard and try to keep him in the gap. If a FB is coming through, stop him in his tracks. The last thing you want the BUCK doing is shedding the blocks, unless the RB is past or nearly past him. If he sheds the blocks early and fails to tackle the back, he made matters worse, now these blockers are in the secondary, the plus one has a blocker coming his way. Not good. The BUCK is supposed to engage blockers, not run around them.  If the BUCK has to take care of an offensive lineman, the best you can hope for is that he holds him up in the gap and doesn’t get blown backward or thrown to the ground. Likewise he should hit the FB back and maintain control of the gap. The BUCK is essentially a small mobile defensive lineman, as it relates to the run, he almost always is part of the gap control scheme and has a gap assigned to him. He did his job if the back has to look elsewhere for an opening and if there are no blockers out in front of him.  The MACK is the playmaker. He often has no gap assigned to him. His job is to seek and destroy the guy with the ball. If the rest of the front did their jobs, he should be free of blockers. If not, he should shed any block immediately or go around them in pursuit of the ball. The MACK is the star of the defense. He should always be around the ball. If he is blocked, the secondary has to make the play which is the last thing a defensive coordinator wants to see.

        I hope this was at least somewhat helpful. Steelers fans are some of the smartest in football, not simply because they're knowledgeable of stats or history, but because they have a solid grasp of what is going on, on the field. The better our understanding, the better fans we can be.